The invention relates to display screens and more particularly, but not exclusively, to projection screens.
It is known from GB-A-2262861 to suggest a panel-form loudspeaker comprising:a
resonant multi-mode radiator element being a unitary sandwich panel formed of two skins of material with a spacing core of transverse cellular construction, wherein the panel is such as to have ratio of bending stiffness (B), in all orientations, to the cube power of panel mass per unit surface area (xcexc) of at least 10;
a mounting means which supports the panel or attaches to it a supporting body, in a free undamped manner;
and an electromechanical drive means coupled to the panel which serves to excite a multi-modal resonance in the radiator panel in response to an electrical input within a working frequency band for the loudspeaker.
U.S. Pat. No. 5,025,474 of MATSUSHITA discloses a projection screen/loudspeaker combination in which the loudspeaker comprises a box-like enclosure formed with ports so that the loudspeaker operates as a bass-reflex speaker to enhance its low frequency performance.
U.S. Pat. No. 3,247,925 of WARNAKA discloses what purports to be a low frequency resonant panel loudspeaker mounted in a chassis and excited by an electromechanical transducer mounted on the chassis.
Embodiments of the present invention use members of nature, structure and configuration achievable generally and/or specifically by implementing teachings of our co-pending application Ser. No. 08/707,012. Such members thus have capability to sustain and propagate input vibrational energy by bending waves in operative area(s) extending transversely of thickness often but not necessarily to edges of the member(s); are configured with or without anisotropy of bending stiffness to have resonant mode vibration components distributed over said area(s) beneficially for acoustic coupling with ambient air; and have predetermined preferential locations or sites within said area for transducer means, particularly operationally active or moving part(s) thereof effective in relation to acoustic vibrational activity in said area(s) and signals, usually electrical, corresponding to acoustic content of such vibrational activity. Uses are envisaged in co-pending application Ser. No. 08/707,012 for such members as or in xe2x80x9cpassivexe2x80x9d acoustic devices without transducer means, such as for reverberation or for acoustic filtering or for acoustically xe2x80x9cvoicingxe2x80x9d a space or room; and as or in xe2x80x9cactivexe2x80x9d acoustic devices with transducer means, such as in a remarkably wide range of sources of sound or loudspeakers when supplied with input signals to be converted to said sound, or in such as microphones when exposed to sound to be converted into other signals.
This invention is particularly concerned with display screens incorporating acoustic devices e.g. in the form of loudspeakers.
Members as above are herein called distributed mode acoustic radiators and are intended to be characterised as in the above co-pending patent application and/or otherwise as specifically provided herein.
The invention is a display screen comprising a panel having a light reflective or light emitting surface, characterised in that the screen comprises a member having capability to sustain and propagate input vibrational energy by bending waves in at least one operative area extending transversely of thickness to have resonant mode vibration components distributed over said at least one area and have predetermined preferential locations or sites within said area for transducer means and having a transducer mounted wholly and exclusively on said member at one of said locations or sites to vibrate the member to cause it to resonate forming an acoustic radiator which provides an acoustic output when resonating. The radiator may comprise a stiff lightweight panel having a cellular core sandwiched between a pair of high modulus skins. The cellular core may be of honeycomb aluminium foil. The skins may be of fibre reinforced plastics. The display screen may comprise a frame surrounding the panel. A resilient suspension may mount the panel in the frame. Panel-form loudspeakers may be attached to opposite sides of the frame to provide left and right hand channel information. The left and right hand loudspeakers may be hinged on the frame to be foldable against the radiator (2) for storage. The left and right hand loudspeakers may each comprise a member having capability to sustain and propagate input vibrational energy by bending waves in at least one operative area extending transversely of thickness to have resonant mode vibration components distributed over said at least one area and have predetermined preferential locations or sites within said area for transducer means and having a transducer mounted wholly and exclusively on said member at one of said locations or sites to vibrate the member to cause it to resonate forming an acoustic radiator which provides an acoustic output when resonating. The screen may be a projection screen.
From another aspect the invention is audio visual apparatus characterised by a projection screen. The audio visual apparatus may comprise at least one rear channel loudspeaker comprising a member having capability to sustain and propagate input vibrational energy by bending waves in at least one operative area extending transversely of thickness to have resonant mode vibration components distributed over said at least one area and have predetermined preferential locations or sites within said area for transducer means and having a transducer mounted wholly and exclusively on said member at one of said locations or sites to vibrate the member to cause it to resonate forming an acoustic radiator which provides an acoustic output when resonating.